1. Field of the Invention
The present invention relates to an electrogastrograph and a method for analyzing data obtained by the electrogastrograph, wherein the electrogastrograph is an apparatus for measuring an electric signal (hereinafter referred to as the stomach signal) produced in the stomach when the stomach goes into action.
2. Description of the Related Art
Heretofore, it has been known to use a method for measuring such stomach signal derived from the stomach's action, in which method, only frequency bands containing the stomach signal are obtained through combination of low-pass filters with high-pass filters, wherein the low-pass filters are used to remove essentially breath signals, and the high-pass filters are used to remove essentially the influence of the body action, so that only the frequency bands containing the stomach signal thus obtained are recorded in a suitable storage medium. In this case, the stomach's action produces 9 slow wave signal that occurs approximately three times a minute, and is very small in variation in its cycle. Consequently, in order to find out or extract the cycle of the stomach signal thus measured, peak frequencies resulted from the Fourier transform such as FFT and like transforms of the thus measured stomach signal are used.
Now, problems to be solved by the present invention will be described.
In general, in order to evaluate the stomach's action, 0.1 cpm (i.e., cycle/minute) resolution is required. In order to achieve this resolution, it is necessary for the conventional Fourier transform to use the amount of data obtained over a period of 10 minutes. Furthermore, the thus obtained result shows an average value of the data obtained over the period of 10 minutes. However, in general, the stomach's action varies drastically in two or three minutes. Consequently, it is not possible for the conventional Fourier transform to process such drastic variations in the stomach's action.
The stomach signal taken out of an electrode attached to a human body surface is feeble, and, therefore always suffers from a relatively high level noise even when the high-pass filters are used to remove the influence which the body action exercises on the stomach signal. When the stomach signal mixed with such noise is subjected to the Fourier transform, its noise components become dominant over all the others to hidden the stomach signal therein, which means that it is impossible to analyze the stomach signal over an extended period of time, for example such as twenty minutes in total before and after noise mixture occurs. However, in a real life, it is substantially impossible to prevent such a noise derived from the body action from entering the stomach signal over such an extended period of time, for example, over twenty minutes in total. Consequently, in the conventional method, it is substantially impossible to analyze the stomach signal occurring in the real life.